Allow not providing typingInstaller to tsserver ProjectService

[JoshuaKGoldberg]

Suggestion

🔍 Search Terms

typingInstaller tsserver ProjectService

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Porting @sheetalkamat's comment from https://github.com/typescript-eslint/typescript-eslint/pull/6754/files#r1161949194:

Even though API doesnt say so you can pass typingInstaller as undefined. We probably need to update the API on our side to reflect that.

📃 Motivating Example

typescript-eslint/typescript-eslint#6754

💻 Use Cases

In https://github.com/typescript-eslint/typescript-eslint/pull/6754/files#diff-48a0545adecca3dfc410b60a48d9665bca5d6124695f462ba16905ec23a9d722R45 I provided an object with empty functions, etc. - but undefined apparently should work too? That'd be much more convenient (& less confusing) on our end as an implementer, trying to instantiate a new project service.